This invention generally relates to thermal inkjet printing. More particularly, this invention relates to the apparatus and process of manufacturing a heat-sink used to cool a resistor or other energy dissipation device used to eject fluid from a fully integrated fluid jet printhead.
Inkjet printers or plotters typically have a printhead mounted on a carriage that traverses back and forth across the width of the paper or other medium feeding through the printer or plotter. Ink (or other fluid) filled channels feed a set of orifices on the printhead surface with ink from reservoir ink source. Energy, applied individually to addressable resistors or other energy dissipating element such as a piezoelectric actuator, transfers energy to the ink within the orifices causing the ink to bubble and thus eject ink out of the orifice towards the paper. As the ink is ejected, the bubble collapses and more ink fills the channels from the reservoir, allowing for repetition of the ink ejection.
Customer demands and competitive pressure continue to drive the need for faster printing and higher resolution. Therefore, there is a strong desire to increase the repetition rate at which the ink ejects from the printhead. Increasing the repetition rate requires that more energy be applied to the resistors in the printhead, thereby causing the printhead to become hotter. If the printhead becomes too hot, the ink will not be ejected from the printhead properly or may misfire causing poor print quality. In addition, the printhead may quit functioning, as it is possible to blow a resistor in the printhead similar to blowing a fuse when a circuit overloads. This type of failure creates a terrible inconvenience to the user as the ink cartridge would have to be replaced. Therefore, it is very important to remove heat generated by the resistor more efficiently.
Another problem, which works against cooling the resistor, is the development of an efficient path to move ink from the reservoir of ink to the resistor in the printhead. This path supports the quick refilling of the orifice after the ink ejects onto the paper. Innovative methods of providing this efficient ink path have unfortunately also reduced the amount of material behind the resistor that in the past was able to conduct the residual heat. Thus the technique, which increases the ink flow to increase the repetition rate, is working against the need to cool the resistor to increase the repetition rate.
Yet another factor, which works against cooling the resistor, is the pursuit of higher print densities in order to have higher resolution and the reproduction of photographic quality prints. As the resolution increases, the amount of ink ejected needs to be reduced per orifice and the adjacent orifices moved closer together. This increase in density means that more energy is going to be expended in a smaller area, thus reducing the amount of space and mass required to move the residual heat away.
Since faster printing, higher print density and resistor cooling are all required, a means for resistor cooling is needed that is compatible with the new efficient ink path and higher density of orifices.